A very discreet divorce for the Aga Khan and his wife

The Aga Khan, one of the world's richest men, and his wife the Begum Aga Khan have filed for divorce.

The couple, who married in 1998 and have a four-year-old son, Prince Aly, have decided to end their marriage officially after being separated for 12 months.

Yesterday Begum Inaara, 44, a German citizen who was known as Princess Gabriele Zu Leiningen before the marriage, filed for divorce in London's High Court claiming the relationship had "irretrievably broken down".

Her spokesman, Lord Bell of Bell Pottinger, said: "The Begum considers the separation and divorce proceedings to be private matters and will be making no comment."

It is the second divorce for both parties. The Aga Khan, a British citizen and the spiritual leader of the Ismaili Muslims, divorced his first wife Sally Croker-Poole, a former English model, nine years ago. The billionaire is reputed to have paid a £20 million settlement to the mother of his three children.

His second wife, born Gabriele Homey in Frankfurt, was previously married to Prince Earl-Emich zu Leiningen. They were divorced in 1997.

A year later she married the 67-year-old Aga Khan, at his estate, Aiglemont, north of Paris.

She converted to the Muslim religion, taking the name Inaara, and lives in Berkshire.

Lawyers for the Begum are said to be drawing up a list of who gets what.

It is unclear whether their son will be the subject of a custody battle.

As one of the world's leading racehorse owners and breeders, the Aga is often seen in winning enclosures of racecourses around the world.

It was customary for his wife to join him but she was notably absent from Royal Ascot and the Prix de l'Arc de Triomphe, France's premier race. The Aga Khan was the owner of Shergar, the Derby-winning racehorse who was kidnapped from his Irish stud farm and never seen again.

As well as his 600 race horses, private jets and properties on five continents the Aga owns newspapers, an airline, hotels, factories and a fabulous collection of jewellery and antiques. A friend of the princess in Geneva told the German newspaper Bild: "She has lived apart from him for a year.

"Neither will discuss it - both place a high value on the utmost discretion."

The newspaper also speculates that the Aga Khan's views on women may have also contributed to the breakdown.

He is said to have told the Begum, a former consultant at Unesco in Paris, at the beginning of their marriage: "There's no discussion on this - I determine things, you obey."

A childhood friend of the Aga told the newspaper: "He has always been this way. At first he cannot take his hands away from his woman. No present is too expensive.

"But when he loses enthusiasm for his woman, his heart turns to ice.

"He has millions of followers all over the world and he is all over the world too, living a macho life, doing what he wants when he wants." The Aga Khan, known as K to his friends, was granted the style "His Royal Highness" by the Queen in 1957.

It is not known whether he signed a pre-nuptial agreement with his wife.

The Institute of Ismaili studies says there are 20 million Ismaili Muslims in the world.

The Aga Khan became Imam of the Shia Imami Ismaili Muslims on July 11, 1957, aged 20, succeeding his grandfather.

He is the 49th hereditary Imam of the Shia Imami Ismaili Muslims and a direct descendant of the Prophet Mohammed.

He was born on December 13, 1936, in Geneva. He spent his early childhood in Nairobi, Kenya and then attended Le Rosey School in Switzerland for nine years.

He graduated from Harvard University in 1959 with a degree in Islamic history. His personal wealth is estimated at £6 billion.